Low temperature deposition of silicon-containing films

ABSTRACT

This invention discloses the method of forming silicon nitride, silicon oxynitride, silicon oxide, carbon-doped silicon nitride, carbon-doped silicon oxide and carbon-doped oxynitride films at low deposition temperatures. The silicon containing precursors used for the deposition are monochlorosilane (MCS) and monochloroalkylsilanes. The method is preferably carried out by using plasma enhanced atomic layer deposition, plasma enhanced chemical vapor deposition, and plasma enhanced cyclic chemical vapor deposition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Application No.61/057,891, filed Jun. 2, 2008 and U.S. Provisional Application No.61/058,374, filed Jun. 3, 2008. The disclosures of those provisionalapplications are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Thin films of silicon nitride have been widely used in variousapplications due to their unique physical, chemical and mechanicalproperties. In semiconductor devices particularly, silicon nitride filmsare used as gate insulations, diffusion masks, sidewall spacers,passivation and encapsulation, etc. Typically, silicon nitride filmsused in the Front End of Line (FEOL) are currently deposited by Lowpressure chemical vapor deposition (LPCVD) in a hot wall reactorat >750° C. using dichlorosilane and ammonia. As the lateral andvertical dimensions of Integrate Circuit (IC) continue to shrink,however, there is an increasing demand for silicon nitride films to bedeposited at much lower temperatures (<550° C.) in order to avoidunwanted reaction between Si and metal, and realize ultra-highintegration devices with precise doping profile control.

To grow silicon nitride films at low temperatures, recently, there havebeen reports that the addition of small amount Ge may lead to thereduction of required deposition temperature for silicon nitride films(U.S. Pat. No. 7,119,016 B2). But this may introduce unwanted impurityto the film, causing reliability issues for the devices that the film issuited for, and may also increase the complexity of the depositionprocess and cost.

Recent innovations to improve complementary metal oxide semiconductor(CMOS) transistor performance have created an industry need for strainedceramic layers compatible with current ultra-large scale integration(ULSI) techniques. In particular, channel carrier mobility for negativemetal oxide semiconductor (NMOS) transistors can be increased throughintroduction of tensile uniaxial or biaxial strain on a channel regionof the MOS transistor. Similarly, compressively strained films can beused to realize an enhancement in channel carrier mobility for positivemetal oxide semiconductor (PMOS) transistors. In US Publication2008/0081470A1, a method for forming a strained SiN film and asemiconductor device containing the strained SiN film is disclosed.

BRIEF SUMMARY OF THE INVENTION

The current invention discloses the method of depositing siliconnitride, silicon oxynitride, silicon oxide, carbon-doped siliconnitride, carbon-doped silicon oxide and carbon-doped oxynitride films atlow deposition temperatures. The silicon containing precursors used forthe deposition are monochlorosilane (MCS) and monochloroalkylsilanes.

In accordance with one embodiment, the present invention relates to aprocess to deposit silicon nitride or carbon-doped silicon nitride on asubstrate in a processing chamber, comprising:

-   -   a. contacting the substrate with a nitrogen-containing source to        absorb at least a portion of the nitrogen-containing source on        the substrate;    -   b. purging unabsorbed nitrogen-containing source;    -   c. contacting the substrate with a silicon-containing precursor        to react with the portion of the absorbed nitrogen-containing        source; and    -   d. purging unreacted silicon-containing source;    -   wherein the process is a plasma-enhanced process.

In accordance with another embodiment, the present invention relates toa process to deposit silicon oxide or carbon-doped silicon oxide on asubstrate in a processing chamber, comprising:

-   -   a. contacting the substrate with an oxygen-containing source to        absorb at least a portion of the oxygen-containing source on the        substrate;    -   b. purging unabsorbed oxygen-containing source;    -   c. contacting the substrate with a silicon-containing precursor        to react with the portion of the absorbed oxygen-containing        source; and    -   d. purging unreacted silicon-containing source.

In accordance with another embodiment, the present invention relates toa process to deposit silicon oxynitride or carbon-doped siliconoxynitride on a substrate in a processing chamber, comprising:

-   -   a. contacting the substrate with a mixture of an        oxygen-containing source and a nitrogen-containing source to        absorb at least a portion of the oxygen-containing source and at        least a portion of the nitrogen-containing source on the        substrate;    -   b. purging unabsorbed oxygen-containing source and        nitrogen-containing source;    -   c. contacting the substrate with a silicon-containing precursor        to react with the portion of the absorbed oxygen-containing        source and nitrogen-containing source; and    -   d. purging unreacted silicon-containing source.

The process in the above embodiments is preferably a plasma enhancedprocess, such as plasma enhanced atomic layer deposition (PEALD), plasmaenhanced chemical vapor deposition (PECVD), and plasma enhanced cyclicchemical vapor deposition. The plasma is an in-situ generated plasma ora remotely generated plasma.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 provides the comparative data of wet etching rates of siliconnitride films deposited via PEALD using Monochlorosilane (MCS) andDichlorosilane (DCS).

FIG. 2 provides the comparative data of chloride concentrations analyzedby Secondary Ion Mass Spectroscopy (SIMS) for the ALD silicon nitridefilms deposited at 450° C. under ammonia plasma, using Monochlorosilane(MCS) and Dichlorosilane (DCS).

DETAILED DESCRIPTION OF THE INVENTION

This invention is to address the issue of forming silicon nitride,silicon oxynitride, silicon oxide, carbon-doped silicon nitride,carbon-doped silicon oxide and carbon-doped oxynitride films at lowdeposition temperatures.

Dichlorosilane (DCS) has been widely used in the semiconductorindustries as silicon source to deposit silicon nitride via reactingwith ammonia. The typical deposition temperatures are greater than 550°C. and the by-products are two moles of HCl per DCS. The presentinvention uses monochlorosilane (MCS) to replace DCS to lower down thedeposition temperatures as well as chloride contamination in theresulting films.

TABLE I DE Reaction (kcal/mol) H₃SiCl + NH₂• → H₃SiNH₂ + Cl• (1) 6.755H₃SiCl + NH₂• → H₂SiClNH₂ + H• (2) −16.757 H₃SiCl + NH₂• → H₃SiNH• + HCl(3) 39.742 H₃SiCl + NH₂• → H₂SiClNH• + H₂ (4) 20.208 H₂SiCl₂ + NH₂• →H₂SiClNH₂ + Cl• (5) 2.05 H₂SiCl₂ + NH₂• → HSiCl₂NH₂ + H• (6) −16.498H₂SiCl₂ + NH₂• → H₂SiClNH• + HCl (7) 36.801 H₂SiCl₂ + NH₂• → HSiCl₂NH• +H₂ (8) 20.445 H₂SiClNH₂ + NH₂• → H₂Si(NH₂)₂ + Cl• (9) 7.222 H₂SiClNH₂ +NH₂• → HSiCl(NH₂)₂ + H• (10)  −17.077 H₂SiClNH₂ + NH₂• →H₂Si(NH₂)(NH•) + HCl (11)  41.821 H₂SiClNH₂ + NH₂• → HSiCl(NH₂)(NH•) +H₂ (12)  20.178 HSiCl₂NH₂ + NH₂• → HSiCl(NH₂)₂ + Cl• (13)  1.471HSiCl₂NH₂ + NH₂• → SiCl₂(NH₂)₂ + H• (14)  −19.099 HSiCl₂NH₂ + NH₂• →HSiCl(NH₂)(NH•) + HCl (15)  36.512 HSiCl₂NH₂ + NH₂• → SiCl₂(NH₂)(NH•) +H₂ (16)  18.346

To understand the cyclic chemical vapor deposition or atomic layerdeposition processes of the reactions for DCS and monochlorosilane underammonia plasma, quantum mechanical calculations were conducted usingspin-polarized density functional theory with the PW91exchange-correlation functional. A double numerical atomic orbital basisset augmented with polarization functions was utilized to represent theelectronic structures of the molecular species. The ground statemolecular structures were obtained upon full geometry optimization. Thecalculated thermochemical energies for various reactions of DCS or MCSwith NH₂. radicals generated under ammonia plasma, are shown in Table I.

From the calculated data shown in Table I, it is clear that forreactions with ammonia plasma, to thermochemically break the Si—H bonds(reactions 2, 6, 10), the chemical processes are moderately exothermic.However, to break the Si—Cl bonds via ammonia plasma, the reactions(reactions 1, 5, 9) are all endothermic. It is much easier to break theSi—H bond than the Si—Cl bond for reactions with ammonia plasma,suggesting that the NH₂. radicals would react with the —SiH₃ fragmentsanchored on the semi-fabricated substrate via reacting MCS with thesurface of the substrate much easier than the —SiH₂Cl fragments anchoredby DCS. As a result, the ALD reaction temperatures as well as thechloride contamination can be reduced.

Working Example Silicon Nitride Film

In this working example, a silicon nitride film has been deposited byusing the following steps.

Substrates to be deposited films on were loaded to a hot wall atomiclayer deposition (ALD) reactor. The reactor was flashed with Ar andpumped down to low pressure of less than 0.1 Torr (T) and heated up to atemperature at which film deposition was performed.

MCS (monochlorosilane) as the Si precursor was introduced to the reactorat a fixed flow rate. The reactor was saturated with MCS for a shortfixed time (typically 10 seconds), and then pumped down to 0.1 T,followed by introducing a fixed flow of NH₃. The reactor was againpumped down after NH₃ precursor saturation for a short fixed time(typically 20 seconds). This cycle is repeated until desired filmthickness is achieved.

The plasma power was set at approximately 100 W, and the temperature wasset at approximately 450° C.

The plasma can be a nitrogen plasma, a mixture of nitrogen and hydrogenplasma, or a mixture of nitrogen and argon. The plasma can be generatedin-situ plasma or remotely. The MCS can also be plasma-excited.

FIG. 1 provides the comparative data of wet etching rates of siliconnitride films deposited via PEALD. FIG. 1 shows PEALD film fromMonochrosilane (MCS) is much more etching resistant than that of DCS.

FIG. 2 provides the comparative data of chloride concentrations analyzedby SIMS for the ALD silicon nitride films deposited at 450° C. underammonia plasma. FIG. 2 suggests MCS gives lower chloride content, orlower chloride contamination.

Embodiment 1 Silicon Oxide Film

In this embodiment, a method of forming silicon oxide films comprisesthe following steps.

Substrates to be deposited films on are loaded to a hot wall CVD or ALDreactor. The reactor is flashed with Ar and pumped down to low pressureof less than 2 Torr (T) and heated up to a temperature at which filmdeposition is performed.

For CVD process, a fixed flow rate of MCS (monochlorosilane) as the Siprecursor is introduced to the reactor. A fixed flow of a fixed flow ofozone as oxygen precursor is introduced to the reactor at the same timeas MCS. The flow stops and then the deposition process stops when adesired film thickness is reached.

For ALD or cyclic CVD process, a fixed flow rate of MCS(monochlorosilane) as the Si precursor is introduced to the reactor. Thereactor is saturated with MCS for a short fixed time (typical less than10 seconds), and then pumped down to 2 T, followed by introducing afixed flow of ozone, or a plasma excited O₂. The reactor is again pumpeddown after N precursor saturation for a short fixed time (typical lessthan 10 seconds). This cycle is repeated until desired film thickness isachieved.

The process is preferably a plasma enhanced process, such as plasmaenhanced atomic layer deposition, plasma enhanced chemical vapordeposition, and plasma enhanced cyclic chemical vapor deposition. Theplasma is an in-situ generated plasma or a remotely generated plasma.

The deposition process is carried out at temperature at or below 550° C.

Embodiment 2 Silicon Oxynitride Film

In this embodiment, a method of forming silicon oxynitride filmscomprises the following steps.

Substrates to be deposited films on are loaded to a hot wall CVD or ALDreactor. The reactor is flashed with Ar and pumped down to low pressureof less than 2 T and heated up to a temperature at which film depositionis performed;

For CVD process, a fixed flow rate of MCS (monochlorosilane) as the Siprecursor is introduced to the reactor. A fixed flow of nitrogen sourcesuch as NH₃ and a fixed flow of O₂ as oxygen precursor are introduced tothe reactor at the same time as MCS. The flow stops and then thedeposition process stops when a desired film thickness is reached.

For ALD or cyclic CVD process, a fixed flow rate of MCS(monochlorosilane) as the Si precursor is introduced to the reactor. Thereactor is saturated with MCS for a short fixed time (typical less than10 seconds), and then pumped down to 2 T, followed by introducing afixed flow of O₂ as oxygen precursor and a fixed flow of NH₃. Thereactor is again pumped down after N precursor saturation for a shortfixed time (typical less than 10 seconds). This cycle is repeated untildesired film thickness is achieved.

The process is preferably a plasma enhanced process, such as plasmaenhanced atomic layer deposition, plasma enhanced chemical vapordeposition, and plasma enhanced cyclic chemical vapor deposition. Theplasma is an in-situ generated plasma or a remotely generated plasma.

The deposition process is carried out at temperature at or below 550° C.

Embodiment 3 Carbon-Doped Silicon Nitride Film

In this embodiment, a method of forming carbon-doped silicon nitridefilms comprises the following steps.

Substrates to be deposited films on are loaded to a hot wall CVD or ALDreactor. The reactor is flashed with Ar and pumped down to low pressureof less than 2 T and heated up to a temperature at which film depositionis performed;

For CVD process, a fixed flow rate of monochloroalkylsilane having ageneral formula of ClSiH_(x)R¹ _(n)R² _(m-x) wherein x=1, 2; m=1, 2, 3;n=0, 1, n+m=<3; R¹ and R² are linear, branched or cyclic independentlyselected from the group consisting of alkyl, alkenyl, alkynyl, arylhaving 1-10 carbon atoms; as a Si precursor is introduced to thereactor. A fixed flow of nitrogen source such as NH₃ is introduced tothe reactor at the same time as monochloroalkylsilane. The flow stopsand then the deposition process stops when a desired film thickness isreached.

The process is preferably a plasma enhanced process, such as plasmaenhanced atomic layer deposition, plasma enhanced chemical vapordeposition, and plasma enhanced cyclic chemical vapor deposition. Theplasma is an in-situ generated plasma or a remotely generated plasma.

For ALD or cyclic CVD process, a fixed flow rate of the Si precursordisclosed above, is introduced to the reactor. The reactor is saturatedwith the Si precursor for a short fixed time (typical less than 10seconds), and then pumped down to 2 T, followed by introducing a fixedflow of NH₃. The reactor is again pumped down after N precursorsaturation for a short fixed time (typical less than 10 seconds). Thiscycle is repeated until desired film thickness is achieved.

Examples of monochloroalkylsilane are ClSiMeH₂, ClSiEtH₂, ClSiEt₂H,ClSi(CH═CH₂)H₂, ClSi(CH═CH₂)MeH, ClSi(CH═CH₂)EtH, ClSi(CCH)H₂,ClSi(iso-Pr)₂H, ClSi(sec-Bu)₂H, ClSi(tert-Bu)₂H, ClSi(iso-Pr)H₂,ClSi(sec-Bu)H₂, ClSi(tert-Bu)H₂.

The deposition process is carried out at temperature at or below 550° C.

Embodiment 4 Carbon-Doped Silicon Oxide Film

In this embodiment, a method of forming carbon doped silicon oxide filmscomprises the following steps.

Substrates to be deposited films on are loaded to a hot wall CVD or ALDreactor. The reactor is flashed with Ar and pumped down to low pressureof less than 2 T and heated up to a temperature at which film depositionis performed;

For CVD process, a fixed flow rate of monochloroalkylsilane having ageneral formula of ClSiH_(x)R¹ _(n)R² _(m-x) wherein x=1, 2; m=1, 2, 3;n=0, 1, n+m=<3; R¹ and R² are linear, branched or cyclic independentlyselected from the group consisting of alkyl, alkenyl, alkynyl, arylhaving 1-10 carbon atoms; as Si precursor is introduced to the reactor.A fixed flow of oxygen source such as ozone is introduced to the reactorat the same time as the Si precursor. The flow stops and then thedeposition process stops when a desired film thickness is reached.

The process is preferably a plasma enhanced process, such as plasmaenhanced atomic layer deposition, plasma enhanced chemical vapordeposition, and plasma enhanced cyclic chemical vapor deposition. Theplasma is an in-situ generated plasma or a remotely generated plasma.

For ALD or cyclic CVD process, a fixed flow rate of the Si precursordisclosed above is introduced to the reactor. The reactor is saturatedwith the Si precursor for a short fixed time (typical less than 10seconds), and then pumped down to 2 T, followed by introducing a fixedflow of ozone. The reactor is again pumped down after N precursorsaturation for a short fixed time (typical less than 10 seconds). Thiscycle is repeated until desired film thickness is achieved.

Examples of monochloroalkylsilane are ClSiEtH₂, ClSiEt₂H,ClSi(CH═CH₂)H₂, ClSi(CH═CH₂)MeH, ClSi(CH═CH₂)EtH, ClSi(CCH)H₂,ClSi(iso-Pr)₂H, ClSi(sec-Bu)₂H, ClSi(tert-Bu)₂H, ClSi(iso-Pr)H₂,ClSi(sec-Bu)H₂, ClSi(tert-Bu)H₂.

The deposition process is carried out at temperature at or below 550° C.

Embodiment 5 Carbon-Doped Silicon Oxynitride Film

In this embodiment, a method of forming carbon-doped silicon oxynitridefilms comprises the following steps.

Substrates to be deposited films on are loaded to a hot wall CVD or ALDreactor. The reactor is flashed with Ar and pumped down to low pressureof less than 2 T and heated up to a temperature at which film depositionis performed;

For CVD process, a fixed flow rate of monochloroalkylsilane having ageneral formula of ClSiH_(x)R¹ _(n)R² _(m-x) wherein x=1, 2; m=1, 2, 3;n=0, 1, n+m=<3; R¹ and R² are linear, branched or cyclic independentlyselected from the group consisting of alkyl, alkenyl, alkynyl, arylhaving 1-10 carbon atoms; as Si precursor is introduced to the reactor.A fixed flow of nitrogen source such as NH₃ and a fixed flow of O₂ asoxygen precursor are introduced to the reactor at the same time as theSi precursor. The flow stops and then the deposition process stops whena desired film thickness is reached.

For ALD or cyclic CVD process, a fixed flow rate of the Si precursordisclosed above is introduced to the reactor. The reactor is saturatedwith the Si precursor for a short fixed time (typical less than 10seconds), and then pumped down to 2 T, followed by introducing a fixedflow of ozone. The reactor is again pumped down after N precursorsaturation for a short fixed time (typical less than 10 seconds). Thiscycle is repeated until desired film thickness is achieved.

The process is preferably a plasma enhanced process, such as plasmaenhanced atomic layer deposition, plasma enhanced chemical vapordeposition, and plasma enhanced cyclic chemical vapor deposition. Theplasma is an in-situ generated plasma or a remotely generated plasma.

Examples of monochloroalkylsilane are ClSiEtH₂, ClSiEt₂H,ClSi(CH═CH₂)H₂, ClSi(CH═CH₂)MeH, ClSi(CH═CH₂)EtH, ClSi(CCH)H₂,ClSi(iso-Pr)₂H, ClSi(sec-Bu)₂H, ClSi(tert-Bu)₂H, ClSi(iso-Pr)H₂,ClSi(sec-Bu)H₂, ClSi(tert-Bu)H₂.

The deposition process is carried out at temperature at or below 550° C.

The working example and embodiments of this invention listed above, areexemplary of numerous embodiments that may be made of this invention. Itis contemplated that numerous other configurations of the process may beused, and the materials used in the process may be elected from numerousmaterials other than those specifically disclosed.

1. A process to deposit silicon nitride on a substrate in a processing chamber, comprising: a. contacting the substrate with a nitrogen-containing source to absorb at least a portion of the nitrogen-containing source on the substrate, wherein the contacting is a plasma-enhanced process; b. purging unabsorbed nitrogen-containing source; c. contacting the substrate with a silicon-containing precursor to react with the portion of the absorbed nitrogen-containing source; and d. purging unreacted silicon-containing precursor; wherein the silicon-containing precursor is monochlorosilane and, steps a through d are repeated at least once.
 2. The process of claim 1, wherein the process is selected from the group consisting of plasma enhanced atomic layer deposition, and plasma enhanced cyclic chemical vapor deposition; wherein the plasma is selected from the group consisting of an ammonia plasma, a nitrogen plasma, a mixture of nitrogen and hydrogen plasma, and a mixture of nitrogen and argon plasma; plasma-excited silicon precursor is optional.
 3. The process of claim 2, wherein the plasma is an in-situ generated plasma or a remotely generated plasma.
 4. The process of claim 1 wherein the nitrogen-containing source for depositing silicon nitride is selected from the group consisting of nitrogen, ammonia, hydrazine, monoalkylhydrozine, dialkylhydrozine, and mixtures thereof. 